1. Field of the Invention
This invention relates to improvements in valves and control systems, particularly those adaptable for use in a material handling system of the type utilizing a generally cup-shaped inflatable bag.
2. Description of the Background Art
In commonly owned U.S. Pat. Nos. 4,421,250 and 4,449,646, and copending U.S. patent applications Ser. No. 357,589 filed Mar. 12, 1982, Ser No. 357,592 filed Mar. 12, 1982, now U.S. Pat. No. 4,476,998 and PCT International Publication No. WO82/03839 of Nov. 11, 1982, there are disclosed systems of handling, storing, and discharging bulk material utilizing a generally cup-shaped inflatable bag for assisting in the discharge of material after it stops flowing following discharge to the extent allowed by gravity. In connection with the development of the inventions disclosed in the co-pending applications, it was discovered that there were no suitable valve assemblies and controls needed for controlling the high volume, low pressure air flow required for inflating or deflating the bag.
British Pat. No. 1,144,162 discloses a lined silo in which the liner is expanded by pressure to assist gravity discharge. The fluid pressure control components are shown schematically as a pump, compressor, and three-way valve alternatively connecting the space between the liner and the rigid wall to the pump or compressor. This arrangement has disadvantages in that it lacks automatic controls, lacks means for sensing the end of inflation and deflation cycles and when to turn the system on or off during discharge, and utilizes extra and unneeded components.
There is a need in the art for a relatively high-volume, low-pressure three-conduit fluid flow control valve assembly which can be switched automatically from one cycle to another, i.e., from the inflation cycle to the deflation cycle. It is highy desirable to utilize other than manual controls for changing cycles and to have the valves controlling the conduits through which the inflating and deflating air passes operate quickly and reliably to handle the large volume of low pressure air from a fan, low pressure blower or the like.